Circuit boards are generally used to electrically connect electronic components to one another and at the same time to mechanically hold them. Circuit boards are also used in order to establish an electrical contact between the circuit board and another contact partner, which is not part of the circuit board. Circuit boards include, in general, an electrically non-conductive base material, which includes a plurality of individual strip conductors. Circuit boards of this type are suitable as carriers for electronic components. The circuit boards are usually protected by a surface protector (solder resist) which, with the exception of the contact surfaces, extends over the entire circuit board surface. Virtually every electronic device includes one or more circuit boards, as do electrical hand-held power tools, rechargeable battery packs and/or charging devices for such rechargeable battery packs.
Electrical hand-held power tools are known in principle and are supplied with current via a mains connection. Alternatively, rechargeable battery devices allow for a high flexibility during work, since they are, in particular, independent of mains power. In this way, it is possible to conveniently carry out outdoor work, for example, so that when operating a hand-held power tool, it is frequently provided to use rechargeable battery packs.
Conventional rechargeable battery packs of this type generally include a large number of rechargeable batteries connected in parallel and/or in series, for example, three cylindrically-shaped lithium ion cells connected in series in a rechargeable battery housing, each having 3.6 V with a total voltage of 10.8 V, for example. The rechargeable battery housing may be coupled to the hand-held power tool in a chamber or an interface or the like of the hand-held power tool, the motor being electrically coupled to the rechargeable battery pack when coupling the two housings and supplying the energy necessary for operating a hand-held power tool.
Thus, within the scope of the present application, a rechargeable battery pack is understood to mean a rechargeable battery pack preferably made up of multiple electrically interconnected rechargeable cells, which is able to store electrical energy. The rechargeable cells are connected both via an electrical connection as well as via a mechanical connection to a circuit board of rechargeable battery pack electronics.
In principle, it is unproblematic to manufacture a circuit board having an oxide-free surface, since there are coating methods for such purpose, for example, using gold, which enable a good contactability without insulating oxides. Circuit boards of this type are expensive.
Alternatively, less precious metals may be used. In these metals, the oxide layer, frequently only a few atomic layers thick, proves to be disadvantageous, since the surface must be pretreated, for example, by chemically or mechanically removing the oxide just prior to the joining of the contact surfaces, or by coating with a chemically stable, electrically conductive layer such as, for example, a graphite layer or gold layer, in order to enable a reliable contacting.